Bullet and method for expanding a bullet

ABSTRACT

During impact of an opening solid-material bullet, a slightly concave or substantially blunt-nosed nose structure of at most 1.2× caliber is provided to such a bullet by mushrooming to generate a blast wave. The bullet opens to a size that is 1.1 to 1.15× caliber. The mushrooming is achieved by arranging on the nose of the bullet a cavity that is in the direction of the center axis of the bullet and has a substantially even-sized diameter.

BACKGROUND OF THE INVENTION

The present invention relates to a bullet according to the preamble of claim 1 and a method according to the preamble of claim 6 for providing the expansion of a bullet when it hits its target. This type of bullet is especially well suited for hunting big game, where it is important that the bullet expands, but it is also necessary to avoid excessive fragmentation of the bullet.

When a sharp-nosed bullet advances in its target, in the muscle mass of a game animal, for example, it displaces tissue on its way. This displacement time of the tissue caused by the bullet corresponds to a time, in which the bullet travels at its advancing velocity a distance, during which the tissue displaces from the nose of the bullet to the biggest outer diameter of the bullet. The shorter this displacement time is, the bigger a blast wave the bullet generates and, at the same time, the bigger the cavitation bubble following the bullet and the trauma caused by the hit become. In practice, this means that the higher flying velocity of the bullet increases the trauma generated in the game animal being hunted, because the time, during which the tissue must move, decreases as the flying velocity increases. On the other hand, a sharper nose on the bullet reduces the trauma, because the time, during which the tissue must move, increases as the nose lengthens.

The cavitation bubble generated by the bullet also makes its advancement instable, because the cavitation bubble prevents the tissue mass it penetrates from supporting the bullet on the sides. In addition, the centre of gravity of the bullet is in the advancing direction behind the midpoint, whereby the offset of the bullet from its direction of travel generates two force components that annul the gyro force caused by the axial rotation of the bullet. Pressure from the surrounding tissue mass will be directed to a part of the side surface of a bullet diverging from its direction, while the moment of the centre of gravity of the bullet increases in relation to the midpoint. As a result of this, the bullet rotates around its longitudinal axis, which results in an unforeseeable direction of travel and a very small penetration.

To increase the trauma resulting from the impact, it is known per se to use partially jacketed or full-jacket rapidly-expanding—also known as mushrooming—bullets in hunting. This is actually in accordance with the hunting act and decree in several countries. This type of mushrooming bullet endeavours to produce a diameter that is clearly larger than the calibre of the bullet and that would cause a bigger blast wave and cavitation bubble and, consequently, a bigger trauma than the original sharp-nosed bullet. This way, the killing power of the bullet can be significantly increased. The killing power of a mushrooming bullet increases for two reasons, in particular. On one hand, the displacement time of the tissue becomes shorter, because the end of the bullet becomes a semi-circular planar surface. On the other hand, the surface area of the bullet contacting the tissue is larger, whereby the generated blast wave is bigger. An embodiment of such a bullet is disclosed in published patent EP1355119.

However, there are significant drawbacks related to the use of these prior-art bullets.

Strongly mushrooming bullets of this type have shown varying deformability that is dependent on impact velocity and the location of the impact. As a result of this, the bullet may pass through the target without opening, or it may open too much or even break. This type of bullet also produces a very strong blast wave that results in tissue damage on the surface of the target and a very limited penetration as a consequence of the decrease in velocity. The bullet then mainly heavily mangles the body parts in the impact area of the game. This damage caused by the bullet in turn lead to the fact that some of the felled game is inedible either due to the deformations or the bullet fragments in it.

The problems described above have been corrected by using blunt-nosed bullets or bullets that become blunt-nosed during impact. However, such bullets that become blunt-nosed require high velocity during shooting to ensure their deformation. This results in similar damage to the game as with the mushrooming bullets described above, because the bullet opens momentarily into the same shape as the present mushrooming bullets.

Some of the bullets manufactured as blunt-nosed bullets have good performance, though. However, these bullets have very bad external ballistics that leads to a more curved trajectory than is usual. Blunt-nosed bullets of this type are mainly only suited for break-action weapons, because due to their structure they feed poorly from the chamber to the breech.

BRIEF DESCRIPTION OF THE INVENTION

It is thus an object of the invention to develop a method for expanding a bullet and a bullet implementing the method so as to significantly reduce the above-mentioned problems.

This object is achieved in such a manner that the bullet and method for expanding the bullet has the characteristics defined in the claims of the present invention. More specifically, the bullet of the invention is mainly characterised by what is stated in the characterising part of claim 1. The method of the invention is, in turn, mainly characterised by what is stated in the characterising part of claim 6.

Preferred embodiments of the invention are disclosed in the dependent claims.

The basic idea of the invention is to provide a cylindrical solid-material bullet that has good ballistic properties and that as a result of an impact turns into a substantially blunt-nosed bullet, however, with clearly less mushrooming in comparison with the earlier bullets.

This type of substantially blunt-nosed or slightly concavenosed bullet provides an as short displacement time of tissue mass as possible in the targeted game animal due to the substantially planar surface formed on the nose of the bullet. A blunt-nosed or slightly concave bullet generates a strong blast wave as it advances in the tissue mass. At the same time, the small surface area of the nose of the bullet impacting the tissue mass leads to a low advancing resistance and high penetration of the bullet.

Such a bullet according to the invention displaces tissue mass rapidly, in which case the strong blast wave it generates has the strongest effect on liquid-containing tissues, such as lungs. As the cavitation bubble formed by the bullet in the muscle tissue is smaller than before, tissue damage to the muscle mass also remain smaller than before.

When the present bullet impacts, a better than before stability is achieved, because the shape of the front surface of the bullet is a symmetrical plane and because the centre of gravity is, differing from earlier, essentially in the midpoint of the bullet. In addition the symmetry of the front surface further diminishes the turning forces acting on the bullet as the impact angle of the bullet changes, and the gyro force caused by the rotation is not cancelled. The result is a deep linearly advancing penetration without a change in direction.

On the basis of conducted tests, it has been detected that a so-called solid-material bullet can successfully be replaced by an only slightly mushrooming solid bullet of the invention without losing killing power. By replacing the strong flesh-destroying cavitation effect generated by the large mushroom of prior-art bullets with a controlled blast wave, it is also possible to successfully minimize the all too common flesh damage in hunting.

This way, a bullet is produced that makes it possible to shoot with the same weapon and bullet both small deer, without making it inedible, and African dangerous game, providing the used calibre is sufficient for the purpose. At the same time, the bullet is designed to meet the requirements of the Nordic hunting legislation to a sufficient extent.

Other advantages of the invention are disclosed in the following, where specific embodiments of the invention are described in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, some preferred embodiments of the invention will be explained in more detail with reference to the accompanying drawing, in which

FIG. 1 is a schematic representation of cavitation bubbles generated by a strongly mushrooming bullet and by a bullet of the invention,

FIG. 2 shows the penetration of a bullet according to an embodiment of the invention in conducted test firings,

FIG. 3 shows a side view of a bullet according to an embodiment of the invention,

FIG. 4 shows the nose of the bullet of FIG. 3 partially and schematically cut,

FIG. 5 shows another schematic cross-section of the nose of the bullet of FIG. 3, and

FIGS. 6 to 9 show the operation of a bullet according to the invention in a situation after impact.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present figures do not show the bullet and method for expanding the bullet in scale, but the figures are schematic and illustrate the structure and operation of the preferred embodiments in principle. Structural parts indicated by reference numerals in the accompanying figures then correspond to structural parts provided with reference numerals in this specification.

When designing the present bullet, the starting point was to create a bullet 1 that combines good terminal ballistics, minor flesh damage regardless of the impact, good feed reliability in all weapons, even in semiautomatics, and sufficient external ballistics and muzzle velocity so as to achieve a firing distance of at least 300 m with so-called normal calibres.

The above goals are achieved by a solid-material bullet that does not have a separate plastic nose that could bend, detach or cause imbalance. The bullet 1 also has a longish smooth nose 2 that is sufficiently small to achieve reliable feed and good external ballistics in the weapon.

The design goals have been reached by providing an opening solid-material bullet 1, which during impact creates a slightly concave or substantially blunt nose structure of at most 1.2× calibre to generate the blast wave. In conducted tests, it has been found that an advantageous result is achieved by a bullet with a nose opening to a size of 0.9 to 1.2× calibre. An especially advantageous result is achieved when the nose of the bullet opens to a size of 1.1 to 1.15× calibre.

The behaviour of the bullet 1 according FIGS. 1 and 2 requires that the nose 2 of the bullet mushroom slightly, but not excessively. When the calibre is sufficiently large, the required mushrooming is achieved by arranging on the nose of the bullet a cavity 4 in the direction of the centre axis 3 of the bullet and with a substantially even-sized diameter d. FIG. 1 shows with a dashed line the operation of a strongly mushrooming prior-art bullet. The solid line, in turn, shows the operation of the bullet of the present solution with smaller mushrooming.

As the bullet 1 hits its target, the pressure F directed to it is adapted to act on the mushrooming of the nose 2, whereby a mushroom 5 forms on the nose and preferably reaches a size that is at most 1.2× the diameter of the bullet body.

As muzzle velocities increase and the calibre becomes smaller, a situation arises, in which the stress of the bullet 1 nose 2 is very strong and finally the formed first mushroom 5 a endeavours to fragment. This type of event is described in the attached FIGS. 6 to 8. However, in such a case, the diameter of the remaining head of the bullet would be too small and it would be too much in front to keep the bullet stable. Attempts have been made to solve the arisen problem by allowing the nose of the bullet to mushroom at least twice as it impacts with the target, see FIGS. 8 and 9. This type of mushrooming is achieved by forming the cavity 4 in the body of the bullet of preferably two cavity parts 6 and 7. In their preferred embodiment, these cavities are produced by consecutive drillings, for example. An example of such a bullet is shown in FIG. 4 that shows two substantially cylindrical drillings. The nose-side cavity 6 is wider than the next cavity 7 and a step-shaped discontinuity area 8 is formed between them.

The cavity provided on the nose of the bullet is clearly shorter in total length L₁ than the calibre of the bullet, that is, in small calibres (approximately 6 to 7 mm in hunting) it is at most 70% of the calibre, and in large calibres (approximately 11 to 12 mm in hunting) it is approximately 40% of the calibre. It has also been detected that when forming the cavity 4 of several cavity parts 6 and 7, it is advantageous to arrange the last cavity to be clearly shorter than the previous one. Thus, L₁−L₂>>L₂. Such a last part of the cavity can also be made to narrow conically.

By making the diameter of each cavity part 6 and 7 smaller than the preceding one in the direction away from the outermost tip, it is possible to control the fragmenting of the created mushrooms 5 a and 5 b. Thus, the bullet 1 according to FIG. 4, for instance, behaves in the manner shown in FIGS. 6 to 9. In such a case, the first mushrooming takes place in the bullet right after is has hit its target. See the mushroom 5 a in the figures. The mushrooming is caused by tissue mass that presses by force F into the cavity 4 in the bullet. As the bullet presses into the tissue mass, it mushrooms naturally at a point where the material strengths of the nose 2 are the smallest, i.e. in the figure, this is the step-shaped point 8, in which two consecutive cavity parts 6 and 7 meet. At this time, the mushrooming comprises both bending of the material surrounding the cavity part 6 and stretching of the material neck 9 at the step-shaped point 8, see FIG. 7. The mushrooming is also assisted by a sufficient difference in the diameters d of consecutive cavity parts, when these are used. When the difference is too small, consecutive mushrooming cannot take place, and the mushrooming extends immediately over the entire length L₁ of the cavity 4. Thus, reliable effectuation of consecutive mushrooming requires that d₂<<d₁.

As the velocity of the bullet slightly decreases as a result of the expansion of the bullet nose, and as the pressure directed to it slightly increases at the same time, the first mushroom 5 a detaches from the discontinuity area 8 on the nose, see FIG. 8. After this, the effect of the force F caused by the tissue mass is immediately directed to the next part 7 of the cavity on the nose and expands the nose with the second mushroom 5 b, which is formed by means of it, into a size of at most 1.2× the diameter of the body, see FIGS. 8 and 9.

At extremely high muzzle velocities and/or small calibres, several consecutive cavities 4 can be arranged at the nose 2 of the bullet 1. This way, one mushroom at a time fragments from the nose as the velocity of the bullet decreases evenly as shown in FIG. 2. At the same time, an even blast wave can be maintained, thus making its expansion into the surrounding tissue mass more controlled than before in accordance with FIG. 1.

The fragmenting of the mushroom 5 a produced on the nose 2 of the bullet 1 can also be assisted by arranging a shoulder 10 according to FIG. 5 or some other discontinuity area of the surface arc of the bullet on the nose of the bullet essentially at the boundary of each consecutive cavity part. This type of shoulder reduces the material strength of the area and assists in a natural manner the fragmenting of the mushroom. This type of shoulder to be formed on the outer surface of the nose in accordance with FIG. 5 can also be replaced by a weakening 10 of a groove-like material neck 9 formed at the bottom of a cavity provided on the nose and/or at the joint of consecutive cavities.

When manufacturing the bullet 1 of a solid material, it is advantageous to arrange at least two parallel grooves 13 on a jacket 12 of the body 11 of the bullet, in the area outside the nose, to prevent excessive pressure from forming in the barrel of the firing weapon.

A preferred embodiment for said solid material and, thus, for the body of the bullet is brass.

It is to be understood that the above description and the related figures are only intended to illustrate the present solution. The solution is thus not restricted to the embodiment described above or defined in the claims, but it will be obvious to a person skilled in the art that a variety of variations and modifications are possible within the scope of the idea defined in the accompanying claims. 

1-9. (canceled)
 10. A hunting bullet that comprises a body made of solid material metal and has on a nose thereof and in a center axis thereof a substantially cylindrical cavity that comprises at least two consecutive cavity parts, wherein a diameter of the nose of the bullet is arranged to mushroom under the effect of a pressure directed to the nose as the nose hits a target, wherein, in a direction away from the nose, a diameter of each cavity part is smaller than a preceding cavity part, wherein the at least two consecutive cavity parts are formed in such a manner that in the direction away from the nose, the diameter of a next cavity part is smaller than the diameter of the preceding cavity part, thus forming a step-shaped discontinuity area, wherein the consecutive cavity parts are of a length, in which a total cavity length is 40 to 70% of a caliber of the bullet, the length of the cavity part on the nose side being longer than the length of the next cavity part, and wherein the discontinuity area of the at least two consecutive cavity parts are arranged to form a mushrooming after hitting the target, whereby the diameter of the nose is adapted to reach a size that is at most 1.2× the caliber of the bullet, and to produce a shape for the nose that is slightly concave or substantially blunt-shaped.
 11. The hunting bullet as claimed in claim 10, wherein, when hitting the target, the diameter of the bullet nose is adapted to reach a size that is at best 1.1 to 1.15× the caliber of the bullet.
 12. The hunting bullet as claimed in claim 10, wherein, when hitting the target, the bullet nose is adapted to mushroom consecutive, the mushrooming appearing at least twice.
 13. The hunting bullet as claimed in claim 12, wherein the mushrooming of the nose of the bullet to 1.1 to 1.15× the caliber of the bullet is adapted to take place substantially at a boundary of each consecutive cavity part, and wherein a continued mushrooming in a direction away from the nose is arranged to provide a controlled fragmentation of the previous mushrooming point at each discontinuity area of each consecutive cavity part.
 14. The hunting bullet as claimed in claim 13, wherein a groove-like weakening of a material neck is arranged on the bullet nose at the bottom of the cavity and/or at a joint of consecutive cavity parts.
 15. The hunting bullet as claimed in claim 11, wherein, when hitting the target, the bullet nose is adapted to mushroom consecutive, the mushrooming appearing at least twice. 